Proper style is to use a prefix in the denominator only if the resulting denominator is equivalent to a coherent unit (in particular, kilograms are used in denominators).
Strangely, Chapter 5 of the SI Brochure is silent on that, Pierre. At least, I could find nothing on the matter. When you describe this "proper" style, which standard are you using for your reference? Would you please provide a quote of its statement to that effect and it's clause or section number?
I think that SI 10 and NIST SP 811 have some words along the lines of what you assert, but they are not quite as specific as you are.
There are many editorial reasons why your guidance is sometimes disregarded by editors. For example, in tables of similar data, one might use the same denominator throughout to keep from forcing the reader to mentally rescale each line.
In the case of medical data, such as blood analyses, the use of the deciliter and the milliliter are perhaps the most common denominators in the U.S.
Jim On 2015-02-09 23:52, Pierre Abbat wrote:
This is in response to Sheri Porter's post on 2014-10-22, which I just found out about. I would like the American medical profession to adopt the metric system, and proper use thereof, as soon as possible. Two examples: When I visit the doctor, she measures my mass and temperature, among other things. This should be done in kilograms and degrees Celsius, which are the units I use at home and the units used all over the world. Measuring mass in kilograms and height in meters would facilitate the calculation of BMI, which is, and has always been, metric. I recently had my hormones measured. Free testosterone was quoted in picograms per milliliter, while total testosterone was quoted in nanograms per deciliter. Using different prefixes in both numerator and denominator makes them difficult to compare and constitutes abuse of the metric system. Proper style is to use a prefix in the denominator only if the resulting denominator is equivalent to a coherent unit (in particular, kilograms are used in denominators). Thus both figures should be quoted in nanograms per liter or, equivalently, in micrograms per kiloliter (since 1 kL=1m³). The common medical use of the deciliter in the denominator should be deprecated. Pierre Abbat
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